The present invention generally relates to a joint or coupling and more particularly, to a rotary joint suitable for coupling a rotating liquid feed tube especially feeding a liquid in a very small amount under high pressure, with a stationary liquid feed tube.
Conventionally, the rotary joint is employed in a centrifugal counter-current distribution chromatograph apparatus disclosed, for example, in Japanese Patent Publication Tokkosho No. 58-1386, Japanese Patent Laid-Open Application Tokkaisho No. 56-10884, or Japanese Utility Model Laid-Open Application Jikkuisho No. 57-70162.
The centrifugal counter-current distribution chromatograph apparatus as referred to above includes a rotary unit, and a large number of columns or separation tubes forming one continuous fluid passage provided side by side, at upper and lower portions in the rotary unit, with axes of the respective separation tubes being directed in the diametrical direction of the rotary unit. The above fluid passage is connected to external feed tubes and flow-out tubes through rotary joints provided at opposite ends of the axis of said rotary unit, and while rotating together with the rotary unit, arranged to be continuously supplied with sample fluid through the feed tube so as to discharge the sample fluid into the flow-out tube through the separation tubes.
By the above arrangement, the counter-current distribution is effected in such a manner that, with the rotary unit in which a stationary liquid having a large specific gravity is preliminarily filled within the separation tubes being rotated, a moving liquid having a small specific gravity is fed under pressure into the separation tubes. In other words, under a centrifugal acceleration field, within the separation tubes, the moving liquid with the small specific gravity is displaced in the form of small particles, through the stationary liquid having the large specific gravity in a direction toward the rotary axis opposite to the direction of the centrifugal force. In the process o the above displacement, the composition readily soluble the stationary liquid and contained in the moving liquid, is dissolved into the stationary liquid, and after the composition readily soluble into the stationary liquid been removed through repetition of the above counter-current distribution per each separation tube, the moving liquid flows into the flow-out tube.
As is seen from the above description, the apparatus of this kind is arranged to continuously effect mixing and separation of the stationary liquid and moving liquid under the centrifugal acceleration field, thereby to remove from the moving liquid, the composition readily soluble into the stationary liquid.
In the chromatograph apparatus having the construction as described above, each rotary joint is intended to connect together the flow passages, each one at the rotary member side and the stationary side, and only the moving liquid flows through the passages, with the stationary liquid staying within the separation tubes.
Accordingly, as the counter-current distribution is repeated, the concentration of the dissolved composition in the stationary liquid reaches a saturated state.
Therefore, when the counter-current distribution is repeated, it becomes necessary to first suspend the distribution work, and stop the supply of the moving liquid so as to refill a fresh stationary liquid, with the used stationary liquid being removed from the interior of the separation tubes, thus rendering the operation to be of a batch type, with a consequent reduction of the working efficiency.
Furthermore, in the known apparatus as described so far, there has been the problem that, even in the case where it is necessary to check the state of the concentration distribution of the dissolved composition in the stationary liquid per each separation tube, the distribution of the above concentration is undesirably disturbed during withdrawal of the stationary liquid from the separation tube, thus making it impossible to check the state correctly.